Workload Domains and vSphere Cluster Design

The vCenter Server functionality is distributed across a minimum of two workload domains and two vSphere clusters. This solution uses two vCenter Server instances: one for the management domain and another for the first compute workload domain. The compute workload domain can contain multiple Cell Site ESXi Hosts.

The cluster design at RDC must consider the workloads that the cluster handles. Different cluster types in this design have different characteristics. When you design the cluster layout in vSphere, consider the following guidelines:

• Use a few large-sized ESXi hosts or more small-sized ESXi hosts for Regional Data Center (RDC)

  • A scale-up cluster has few large-sized ESXi hosts.

  • A scale-out cluster has more small-sized ESXi hosts.

• Use the ESXi hosts that are sized appropriately for your Cell Site locations.

• Consider the total number of ESXi hosts and cluster limits as per vCenter Server Maximums.

vSphere High Availability

VMware vSphere High Availability (vSphere HA) protects your VMs in case of an ESXi host failure by restarting VMs on other hosts in the cluster. During the cluster configuration, the ESXi hosts elect a primary ESXi host. The primary ESXi host communicates with the vCenter Server system and monitors the VMs and secondary ESXi hosts in the cluster.

The primary ESXi host detects different types of failure:

• ESXi host failure, for example, an unexpected power failure.

• ESXi host network isolation or connectivity failure.

• Loss of storage connectivity.

• Problems with the virtual machine OS availability.

The vSphere HA Admission Control Policy allows an administrator to configure how the cluster determines available resources. In a small vSphere HA cluster, a large proportion of the cluster resources is reserved to accommodate ESXi host failures, based on the selected policy.

However, with a Regional Data Center and a Cell Site construct in the Telco Cloud Platform RAN deployment, you need to only enable vSphere High Availability on your workload cluster at Regional Data Center. vSphere HA is not required on your cell site host as it is managed as a standalone host.

Recommended vSphere HA design for Cell Site Host:

Cluster Operation	Locations	Action	Justification
vSphere HA	Cell Site	No HA	Hosts are deployed as standalone at Cell Site without a vSphere Cluster.

vSphere Distributed Resource Scheduler

The distribution and usage of CPU and memory resources for all hosts and VMs in the cluster are continuously monitored. The vSphere Distributed Resource Scheduler (DRS) compares these metrics to an ideal resource usage given the attributes of the cluster’s resource pools and VMs, the current demand, and the imbalance target. DRS then provides recommendations or performs VM migrations accordingly.

Recommended vSphere DRS design for Cell Site Host:

Operation	Location	Action	Justification
DRS	Cell Site	No DRS	Hosts are deployed as standalone at Cell Site without a Cluster.